BANGOR, Maine — The manager of a Chinese buffet-style restaurant in Waterville has waived indictment and pleaded guilty in U.S. District Court to conspiracy charges related to the employment of unauthorized workers, according to information available on the court’s Electronic Case Filing System.

She was released on $5,000 unsecured bond and ordered to surrender her passport.

A sentencing date has not been set.

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Zhang is the second member of her family to be charged in Maine in connection with the employment of unauthorized workers. Mei Ya Zhang, 28, of Brewer was charged in January with conspiracy to harbor illegal aliens for commercial advantage and private financial gain. She has not been indicted.

The younger woman was described in court documents as the manager of the Brewer location. Information on exactly how the two women are related was not available Monday morning. Both are naturalized citizens and nieces of the family patriarch Zi Qian Zhang, who resides in Massachusetts, according to court documents.

The Portland and Lewiston locations remained open Monday. Efforts to determine if the Waterville restaurant still is in operation were unsuccessful Monday.

The investigation, which began in February 2006, revealed that the Zhang organization employed and harbored scores of unauthorized workers at its Chinese buffets and bistros, according to a previously published report. The family allegedly harbored them at 11 safe houses in three states located near the restaurants and ferried them to and from work in vans.

Between June 2008 and mid-November 2011, 18 individuals were identified as being in the U.S. illegally and working at the Waterville restaurant, according to the prosecution version of events to which Mei Juan Zhang pleaded guilty. Each was paid at least $1,300 in cash and received no overtime pay, health insurance, workers’ compensation or other benefits. Most worked 12 hours a day, six days a week.

The restaurant also employed some legal workers, according to court documents. They were paid with payroll checks and reported on the restaurant’s quarterly tax filings. The unauthorized employees were not. The unauthorized workers lived at what was described in court documents as a “safe house” at 7 Oak St. in Waterville. Conditions inside the house were not described but money was deducted from their pay for housing.

Mei Juan Zhang faces up to 20 years in federal prison on the money laundering charge. On the harboring illegal aliens and filing false federal tax return charges, she faces up to 10 years in prison, respectively. In addition, she could be fined a total of $1 million.